We investigated the prevalence of extended spectrum -lactamase (ESBL) producing Escherichia coli in untreated hospital wastewaters and two sewage treatment plants (STPs). A collection of 252 ESBL-producing E. coli isolates from hospital wastewater and STPs were typed and tested for resistance to 17 antimicrobial agents, the presence of integron-associated integrases (intI gene) and ESBL genes. Eighty nine percent (n=176) of the ESBL-producing E. coli strains from hospital waste water were found in more than one sample (common types) with one common type accounting for 35% of isolates, found in all samples. These strains were also resistant to up to 9 non-beta-lactam antibiotics and showed the same pattern of resistance in all samples. More than 73% of the hospital wastewater isolates possessed SHV-type ESBL as opposed to isolates from STPs that carried only CTX-M-type ESBL-genes. The prevalence of intI gene did not differ between isolates from these sources. Certain ESBL-producing E. coli were dominant in hospital wastewaters. These strains possessed -lactamase genes that were different from isolates found in STPs. From a public health point of view, the presence of such a high level of ESBL-producing E. coli strains in hospital wastewaters is of great importance.